*{
    padding: 0;
    margin: 0;
    box-sizing: border-box;
}
.all{
    width: 500px;
    margin: auto;
}
.nav{
    list-style: none;
}
.nav::after{
    display: table;
    content: "";
    clear: both;
}
.nav li{
    cursor: pointer;
    text-align: center;
    width: 100px;
    padding: 10px;
    float: left;
}
.nav > .active{
    border-bottom: 3px solid #F40;
}
.main div{
    display: none;
}
.main > .active{
    display: block;
}